Quantum computer calculates exact energy of molecular hydrogen(eurekalert.org)
eurekalert.org
Quantum computer calculates exact energy of molecular hydrogen
http://www.eurekalert.org/pub_releases/2010-01/hu-qcc010810.php
6 comments
I doubt it will ever stop. It's too appealing for journalists, and a lot easier than explaining the true state of affairs. I have story about this which I can't resist telling. It really annoyed me at the time, but with a few years distance I think it's both funny and illustrative of media stories about quantum computing.
In 2001, I was interviewed about quantum computing by a reporter (from the Sydney Morning Herald, if I recall correctly) who repeatedly asked me for a "simple, concrete explanation" of how quantum computers work.
If you take this request really (really!) literally, such an explanation probably isn't possible. If it was, you could efficiently simulate the elements of the explanation on a conventional computer, and quantum computers would offer no real advantage over conventional computers. In fact, in my opinion, what's interesting about quantum computing is precisely the gap between our ability to give such a simple, concrete explanation and what's really going on. You _can_ give a (fairly) simple indirect explanation of how they work - simple if someone's comfortable with complex numbers and vectors - but it is pretty indirect.
I explained this to the reporter, who made all the right noises, and then gave him the "simultaneously in all possible states" explanation as an example of the kind of nonsense that sounds good, but actually obscures the truth of what's going on.
You can probably guess the rest: when the article came out, I was in there, quoted saying something along the lines of "When a quantum computer is put to work on a problem, it considers all possible answer by simultaneously arranging..."
The problem is that this line is just too tempting and pat a story for reporters. It creates the illusion of understanding (in my opinion), while leaving the more complex truth undisturbed.
In 2001, I was interviewed about quantum computing by a reporter (from the Sydney Morning Herald, if I recall correctly) who repeatedly asked me for a "simple, concrete explanation" of how quantum computers work.
If you take this request really (really!) literally, such an explanation probably isn't possible. If it was, you could efficiently simulate the elements of the explanation on a conventional computer, and quantum computers would offer no real advantage over conventional computers. In fact, in my opinion, what's interesting about quantum computing is precisely the gap between our ability to give such a simple, concrete explanation and what's really going on. You _can_ give a (fairly) simple indirect explanation of how they work - simple if someone's comfortable with complex numbers and vectors - but it is pretty indirect.
I explained this to the reporter, who made all the right noises, and then gave him the "simultaneously in all possible states" explanation as an example of the kind of nonsense that sounds good, but actually obscures the truth of what's going on.
You can probably guess the rest: when the article came out, I was in there, quoted saying something along the lines of "When a quantum computer is put to work on a problem, it considers all possible answer by simultaneously arranging..."
The problem is that this line is just too tempting and pat a story for reporters. It creates the illusion of understanding (in my opinion), while leaving the more complex truth undisturbed.
I've heard this dozens of times, and I know every time that it's crazy.
But I haven't really managed to figure out what part of this 'rumor' is actually true.
Do you mind explaining where this idea comes from, and whether it's remotely right, or what?
But I haven't really managed to figure out what part of this 'rumor' is actually true.
Do you mind explaining where this idea comes from, and whether it's remotely right, or what?
This should clear things up:
http://en.wikipedia.org/wiki/Qubit
Also this: http://www.het.brown.edu/people/andre/qlambda/index.html
but the basic idea is that quantum computers allow operations to be taken on an entire list simultaneously (entanglement).
Also this: http://www.het.brown.edu/people/andre/qlambda/index.html
but the basic idea is that quantum computers allow operations to be taken on an entire list simultaneously (entanglement).
So does hacker news have a problem with quantum mechanics being explainable?
?
?
No. With quantum mechanics being explained wrong.
"This has got to stop."
Popular science journalists always fall back on the simplified multi-universe explanation to explain quantum computing. I wish they would adopt another paradigm too, but in general I want to see a better quality of synopses of technical papers in popular journalism.
Getting back to the subject of the article... Scott Aaronson has always said the most interesting use of quantum computing would be to simulate natural processes. This may be the first significant achievement of that. (At least that I have heard of.)
Popular science journalists always fall back on the simplified multi-universe explanation to explain quantum computing. I wish they would adopt another paradigm too, but in general I want to see a better quality of synopses of technical papers in popular journalism.
Getting back to the subject of the article... Scott Aaronson has always said the most interesting use of quantum computing would be to simulate natural processes. This may be the first significant achievement of that. (At least that I have heard of.)
The many-worlds interpretation of quantum mechanics is a consistent viewpoint that fits with the standard equations of Quantum Mechanics:
http://en.wikipedia.org/wiki/Many-worlds_interpretation
If it also happens to correspond to human intuition, I'm not sure exactly what the problem is.
http://en.wikipedia.org/wiki/Many-worlds_interpretation
If it also happens to correspond to human intuition, I'm not sure exactly what the problem is.
I'm objecting to the dumbed-down version of the many worlds interpretation as an explaination of quantum computing because it gives the impression quantum computing can do things it can't actually do, like solve NP-complete problems efficiently, which is not currently theorized, let alone proven.
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What do you mean?
Quantum mechanics is indeed a different viewpoint
As I recall, the Feynman diagram approach assumes that every conceivable interaction between particles that could happen does happen with a given probability depending on the interaction's complexity.
Indeed, the Heisenberg Uncertainty Principle is quite a mind fuck - if you know the exact speed of a particle, the location of particle become utterly uncertain to the point that it could be anywhere in the universe.
So what specifically is your problem with the above quote?
Quantum mechanics is indeed a different viewpoint
As I recall, the Feynman diagram approach assumes that every conceivable interaction between particles that could happen does happen with a given probability depending on the interaction's complexity.
Indeed, the Heisenberg Uncertainty Principle is quite a mind fuck - if you know the exact speed of a particle, the location of particle become utterly uncertain to the point that it could be anywhere in the universe.
So what specifically is your problem with the above quote?
Your comment is painfully embarrassing to read. Instead of attacking what I said (or me), try asking: "could you elaborate on what you think the article is misrepresenting?".
What is wrong is that a quantum computer doesn't consider all possible answers at the same time. Although the qubits are in a 'combination' of two possible final states. it's not as if each state represents one of the answers to the question. During a computation on your current computer the bits involved in the computation don't evolve towards an answer either (although a subset of them will).
This is an example of quantum simulation, which is considered significantly easier to achieve than general quantum computing.
Several quantum systems can be modeled with other, unrelated quantum systems, to solve the dynamics of those systems. The cannot unfortunately be used for general quantum gate operations that you hear about.
And as usual, for QC stuff, I'll defer any real comments to Michael Nielsen, if he happens to see this submission.
Several quantum systems can be modeled with other, unrelated quantum systems, to solve the dynamics of those systems. The cannot unfortunately be used for general quantum gate operations that you hear about.
And as usual, for QC stuff, I'll defer any real comments to Michael Nielsen, if he happens to see this submission.
This is arguably one of the most important breakthroughs ever in the field of computing.
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If it scale and lives up to the general description it will be. Whether it will do that it another question.
How can I read the full article?
After reading the paper here: http://arxiv.org/pdf/0905.0887, I think that this wasn't actually done on a quantum computer, but rather simulated via PyQuante: http://pyquante.sourceforge.net/#
It's still impressive, but goes to show that we're a long way from practical quantum computing.
It's still impressive, but goes to show that we're a long way from practical quantum computing.
I don't have the time right now to slog through what is probably a very interesting paper, but this did catch my eye "We perform a key algorithmic step the iterative phase estimation algorithm in full, achieving a high level of precision and robustness to error. We implement other
algorithmic steps with assistance from a classical computer and explain how this non-scalable approach could be avoided."
It sounds like they claim at least part of it they did with real quantum computing. Scanning the paper I think they did some calculations on "real" one and two qubit systems.
It sounds like they claim at least part of it they did with real quantum computing. Scanning the paper I think they did some calculations on "real" one and two qubit systems.
Ah yeah, I'm pretty sure you are correct after re-reading that part.
This has got to stop.